I looked at www.lei-extras.com to see if they had a "switchbox" unit that would enable you to use a transom & TM transducers off the one unit. I did not see where any of the switchboxes mentioned, said they would fit your unit. You might want to contact them, though, just to be sure.
Here's the TM transducer selection for your unit : http://www.lei-extras.com/store/sear...s+%26+Adapters
Here's their selection of switchboxes : http://www.lei-extras.com/store/sear...r+Switch+Boxes
I have done business with LEI, and they have served me well. .... cp